Effect of Diet Complexity and Dietary Fish Peptide Supplementation on Weanling Pigs
Type of DegreeMaster's Thesis
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Young pigs are subjected to various stressors at weaning, and providing a highly palatable and digestible diet is, obviously, important in preventing or alleviating growth check soon after weaning and also optimizing growth performance thereafter. Although a corn-soybean meal (SBM) diet is the golden standard for feeding pigs, such a diet may not be appropriate for weanling pigs because of many digestive, metabolic, and immunological challenges. For instance, their enzyme profile is designed to utilize milk protein, carbohydrate, and fat, i.e., not nutrients in corn and SBM. For those reasons, weanling pigs have been fed complex diets that contain many special ingredients such as dried whey, soy protein concentrate, plasma protein, fish meal, blood meal, oat groats, and others. Providing such diets with highly-palatable and highly-digestible ingredients to weanling pigs can be rather costly. However, a small amount of some alternative feed supplement, such as fish peptides, can be included as an alternative source of nutrients for weanling pigs. In addition, such a feed additive may have some bioactive or functional properties than can be beneficial for their health and growth performance. By using such a feed additive, along with a rapidly increasing enzyme technologies in recent years, it might be possible for weanling pigs to utilize corn-SBM diets more efficiency. As part of the project to explore the possibility of replacing complex diets with semi simple or simple corn-SBM diets for weanling pigs, a study was conducted to assess the effect of fish peptides on their growth performance, serum metabolite profile, and serum cytokines. Forty-eight gilts and 48 castrated males (initial body weight, 7.87 ± 0.71 kg) weaned at 3 to 4 wk of age were randomly assigned to 6 dietary treatments with 4 replicate pens (2 gilts and 2 castrated males/pen) per treatment. Because of the availability of pigs and facility at one time, the study was conducted in 2 trials, and each trial used 24 gilts and 24 castrated males. Two trials were approximately 8 wk apart. After weaning, pigs were fed a common pre-starter diet for 4 d before beginning of the study, and a 2-phase feeding program was used. Each phase consisted of 2 wk. Two typical complex, positive control (POS) diets containing various special ingredients were formulated and used as the positive control (POS) diets. Two simple, corn-SBM-based negative control (NEG) diets were formulated to be iso-lysinic to the POS diets, and the NEG diets for both phase 1 and 2 were supplemented with 0, 0.5, 1.0, 1.5, or 2.0% fish peptides. A small amount of dried whey (5%) was included in the phase 1 NEG and fish peptide diets to ensure that pigs were growing. Dried whey was not include in the phase 2 NEG and fish peptide diets. Fish peptides were included in the diet by replacing the part of corn and SBM. All 6 diets were formulated to meet or exceed the 2012 NRC nutrient requirements. Pigs were weighed and feed intake was recorded weekly. During the fourth week of the study, approximately 5 mL of blood was collected from each pig via vena cava puncture using a sterile needle and evacuated tube. Serum was separated, and an aliquot was stored at -20ºC. Serum sample from each pig was analyzed for metabolites, whereas serum samples were pooled by pen and analyzed for serum cytokines. During the last 2 wk of the study, the intake of feed, Lys, and DE increased cubically (P = 0.025, 0.025, and 0.026, respectively) as fish peptide supplementation increased from 0 to 2%. Overall, pigs fed the diets supplemented with 1.5% fish peptides had greater feed, Lys, and DE intakes (approximately 8%) than those fed other diets, but those differences were not statistically significant (cubic, P = 0.135, 0.136, and 0.167 respectively). Overall weight gain of pigs fed the diets containing fish peptides seemed to be greater (6.7%) than those fed the POS diet, but, again, it was not statistically significant (P = 0.137). There were no clear trends in the efficiency of overall utilization of feed, Lys, or DE intake for weight gain. Pigs tended to respond linearly and quadratically (P = 0.092 and 0.106, respectively) to the increase in fish peptide supplementation in serum total protein. Serum urea N concentration was greater in pigs fed the diets supplemented with fish peptides compared with those fed the POS diets (P = 0.005), whereas it increased linearly (P = 0.017) as fish peptide supplementation increased from 0 to 2%. Although pigs tended to respond quadratically (P = 0.093) to fish peptide supplementation in serum triglyceride, there was no clear effect of dietary treatments on serum albumin, globulin, glucose, or cholesterol concentration, or albumin to globulin ratio. Similarly, there was no clear effect of dietary treatments on any of the serum cytokine concentrations. In conclusion, the response patterns of weanling pigs to dietary treatments were rather inconsistent. Pigs did not respond to the complex diets and simple corn-SBM-based diets as expected, and their response to dietary supplementation of 0 to 2% fish peptides to simple corn-SBM-based diets were not consistent. Because of the considerable variations in the data, the effort to estimate the optimum inclusion rate by fitting selected response criteria against various regression models was not successful. Based on the subjective evaluation, however, the greatest values in many response criteria seemed to be observed with pigs fed the diets containing 1.5% fish peptides, even though, again, the response patterns to fish peptide supplementation were rather inconsistent.